Some chimps, especially youngsters and female adults, use spearlike wooden tools to hunt.

By Emily Sohn, 00:00 AM March 2, 2007

Pictures of our ancestors often show men hunting with spears, arrows, and other tools. Scientists have long thought that only humans made tools for the hunt. They've also assumed that men did most of the hunting.

Now, for the first time, scientists have observed wild chimpanzees hunting with tools. What is just as surprising, females and young chimps outnumber males in these hunts. The discovery throws into question many assumptions about human evolution.